Trochanteric and subtrochanteric femur fractures are currently treated with an intramedullary nail having a transverse bore for receiving a bone fastener, such as a femoral neck screw usually provided in the form of a sliding screw. The intramedullary nail is fitted in the intramedullary canal of the femur, and the sliding screw is then passed through the transverse bore of the intramedullary nail, through the neck of the femur and into the femoral head.
The treatment of unstable trochanteric and intertrochanteric fractures, which show an additional basocervical (lateral femoral neck) fracture in combination with an avulsion of the greater trochanter, are still a challenge for internal fixation with a proximal femoral nail. With conventional surgical techniques there is no procedure to avoid a lateralization of the greater trochanter in proximal femoral nailing. To prevent lateralization of the greater trochanter, an additional stabilization is required. Such stabilization may be realized by a trochanter stabilization plate which allows for fixation of an avulsed greater trochanter fragment.
US 2007/0219636 A1 discloses an implant system for proximal femur fractures. The implant system includes an intramedullary nail and an extramedullary buttress plate. The extramedullary plate has an upper transverse part including holes for fastening the plate by screws to the greater trochanter of a femur. The plate further has a lower elongate vertical part with two central holes for receiving proximal sliding hip pins which penetrate proximal holes of the intramedullary nail for compression of bone fragments. A lower part of the plate has small holes for receiving cortical screws to fix the plate to bone. Thus, the extramedullary buttress plate is connected to the intramedullary nail only with the sliding hip pins, resulting in a low construct stability between the pins, screws and plate.
Each of US 2008/0154311 A1 and EP 1 398 000 B1 relates to an implant system with an extramedullary plate and an intramedullary nail. The plate has several openings for receiving bone screws and is fixed to the intramedullary nail by one locking screw inserted through a central through opening of the plate. Then, fixation pins or screws are inserted at different angles to each other into bone through the other holes of the extramedullary plate.
The conventional implant systems have several drawbacks. For example, when the extramedullary plate is tightened with locking screws, a sliding screw inserted through the plate and the intramedullary nail may get jammed, which would cause a canting of the extramedullary plate and the bone screws, since the axes of the bone screws are oblique to each other. Thus, the stability between the extramedullary plate, the bone screws and the intramedullary nail is decreased and a defined sliding of the sliding screw within the intramedullary nail cannot be guaranteed.